1.Field of the Invention
The present invention generally relates to the manufacture of microelectronic systems and, more particularly, to enhancement of the interconnect properties of aluminum and aluminum alloy electrical conductors in fine line width conductor patterns with improved resistance to electromigration.
2.Background Description
Aluminum-based interconnects are commonly used in the industry due to their low resistivity and ease of fabrication. However, such interconnects are less reliable than either tungsten or copper-based interconnects since they are subject to electromigration, where electrical current induces damage in paths such as grain boundaries. Many different types of grain boundaries can form between aluminum grains, depending on their orientations, and different types of grain boundaries have been shown to produce enhanced or degraded reliability. See for example H. P. Longworth and C. V. Thompson, MRS Symp. Proc., Vol. 265, 1992, pp. 95-100.
The "texture" of an aluminum film, as determined using X-ray diffraction, describes the distribution of grain orientations in a film, and hence indicates whether fewer or more types of grain boundaries exist in a film. More types of grain boundaries increase the likelihood that "weak" boundaries will be incorporated in an interconnect after patterning. Hence, the degree of texture in a film is an indication of how well the film will resist electromigration damage. See D. B. Knorr and K. P. Rodbell, SPIE Vol. 1805 Submicrometer Metalization 1992, pp. 120-221.
Effects of insulator surface roughness on Al-alloy film crystallographic orientation in Al-alloy/Ti insulator structures have been discussed by H. Onoda et al., Jpn. J. Appl. Phys., vol. 34 (1995), pp. 1037-1040.